A prolonged and extremely dangerous heat wave continues for much of the Southern Tier of the Lower 48 thanks to an expansive dome of high pressure aloft, where approximately 80 million people could experience an air temperature or heat index above 105 degrees through this weekend.
Article continues below
In light of widespread record breaking heat across the the Southern Tier this past weekend, plenty more record breaking hot weather is expected across the Four Corners states, Texas to the Lower Mississippi Valley, and South Florida through the end of the work week.
Daytime highs will reside in the triple digits in the Desert Southwest and Texas, while the Gulf Coast and Mid-South can expect daytime highs in the upper 90s that coincide with oppressively high dew points, resulting in sweltering heat indices upwards of 120 degrees in places.
Meanwhile, daily low temperatures will remain quite warm, breaking record warm daily minimums in some areas which limits relief from the heat overnight.
Accordingly, an expansive area of Excessive Heat Warnings and Heat Advisories remains in the Southwest, Southern Plains, western and central Gulf Coast, and even parts of South Florida where well above normal sea surface temperatures and lighter than normal winds are contributing to stifling heat.
Please visit heat.gov for more information on impacts from the heat wave.
The Northeast and Mid-Atlantic will continue to see hot and humid conditions through Tuesday (albeit more seasonal), while a cold frontal passage helps to make conditions a little less muggy by Wednesday.
To the west, a pair of cold fronts will provide the Midwest and Great Lakes with cooler than normal temperatures.
Some locations in the Upper Midwest will struggle to get out of the 70s for through midweek.
A stormy couple of days remain on tap from the Midwest to the Ohio and Tennessee Valleys.
Today and into Tuesday night, a quasi-stationary frontal boundary over the Middle Mississippi Valley will be the focus for strong-to-severe storms.
Since overnight, the Storm Prediction Center (SPC) has upgraded to an Enhanced Risk (threat level 3/5) extending across southeast Missouri, southern Illinois, western Kentucky, and Tennessee (including Nashville) for damaging wind gusts, large hail, and tornadoes.
Meanwhile, developing thunderstorms will contain copious amounts of moisture and could train over parts of the region, resulting possibly in dangerous flash flooding.
A Moderate Risk (threat level 3/4) of Excessive Rainfall remains across the Mississippi-Ohio River Confluence to northwest Tennessee, where 5-8" of rainfall is possible where the main axis of training sets up.
There is also a Slight Risk (threat level 2/4) of Excessive Rainfall in the Northeast due to more rounds of thunderstorms in areas that feature highly saturated soils, with some severe wind gusts also possible with this activity.
Elsewhere, SPC maintains a Slight Risk area this afternoon in North Dakota where storms could produce very large hail.
On Wednesday, more showers and storms will form from the central Rockies and Midwest to the Mid-Atlantic.
SPC and WPC both have large Marginal Risk areas in place, while WPC does have a Slight Risk in the Tennessee Valley and southern Appalachians where the threat for flash flooding is greater from saturated soils owing to earlier heavier rainfall.
The threat of heavy rainfall looks to continue into Thursday where scattered flash flooding remains possible across the Appalachians and Northern Mid-Atlantic, with a separate excessive rainfall area also highlighted across the Central High Plains.
West of the Rockies, the Southwest monsoon is showing signs of life with rounds of showers and storms possible each day, where the strongest storms could produce bouts of isolated flash flooding and damaging wind gusts.
In the north central Pacific Ocean, Tropical Storm Calvin is weakening as it approaches Hawaii's Big Island where Tropical Storm Warnings have been issued.
The latest forecast from the Central Pacific Hurricane Center shows the storm maintaining tropical storm status as it tracks south of the Big Island tonight.
The forecast remains on track for Calvin to likely produce locally heavy rainfall with as much as 4-8 inches and localized amounts up to 10 inches along the windward slopes of the Big Island.
A little farther north, 3-6 inches of rainfall are possible along the windward slopes of Maui.
Calvin is also likely to cause rough seas and locally strong winds around "The Aloha State." See Central Pacific Hurricane Center advisories on Calvin for more information on the storm.
Smoke from the Canadian wildfires will remain in the picture through mid-week as northwesterly winds aloft that originate over Canada continue to direct smoke into the Lower 48.
There are Air Quality alerts issued for areas the include the northern High Plains, the Midwest, Great Lakes, southern Mid-Atlantic, and into the Northeast where higher concentrations of smoke will result in unhealthy air quality for sensitive groups. ■
A clipper system will move quickly across the northern Plains into the Midwest Friday and the Northeast by Saturday, bringing a wintry mix of rain and snow showers ahead of a sweeping cold front.